This invention relates generally to injection molding and more particularly to a system in which several nozzles are mounted on the side of an elongated manifold to inject through spaced gates to a common cavity, and a method of manufacturing the nozzles.
Injection molding is being used to make larger and larger components, particularly in the automotive industry. In addition to considerably increasing the size of the melt channel, this has led to the use of systems in which several nozzles extend from an elongated manifold through separate gates to a single cavity. These applications normally necessitate very high injection pressures up to 30-40,000 psi. and require very large molds which are difficult to machine with accuracy. In the past, the nozzles have been mounted along the forward face of an elongated manifold with sealing provided by each nozzle being in bearing contact against a shoulder in the mold cavity plate. However, in view of the large mold size and high melt pressure, it has been found to be very difficult to machine to the necessary tolerances to provide reliable sealing. Also in past valve-gated systems, as shown for instance in the applicants' U.S. Pat. No. 4,530,654 entitled "Injection Molding Peripheral Opening Core Ring Gate" which issued July 23, 1985, the melt flows through each nozzle in a channel around the valve pin. However, for the present high volume, high pressure applications it has been found to be more efficient to use a separate melt flow channel offset from the central valve pin bore.
Frequently, these large elongated cavities are non-linear and it is desirable to mount the nozzles in different positions relative to each other to connect to the manifold. The applicants' Canadian patent application Ser. No. 524,208 filed Dec. 1, 1986 entitled "Side Mounted Manifold Block For Variable Orientation of Injection Molding Nozzle" provided one solution to this problem using "manifold blocks." The present invention provides an alternative solution in which the "manifold blocks" are not necessary.